The subject matter disclosed herein relates to seal systems, and more particularly, to seal systems for rotary machines such as turbomachines.
In general, turbomachines transfer energy between a rotating element, or rotor, and a fluid. In turbines, energy is transferred from the fluid to the rotor and in compressors, energy is transferred from the rotor to the fluid. For example, a steam turbine extracts thermal energy from pressurized steam to perform work to rotate the rotor or shaft. The steam may flow through one or more turbine stages to generate electrical power or energy for a mechanical drive such as a compressor. As the steam passes through the stages, useful work is produced. However, because of the presence of both rotating and stationary parts in the steam turbine, there will be passages where steam leaks through. Alternatively, there will be a leakage path between the rotating and static parts and that leakage path is affected by the seal configuration and the radial gap between these parts. Additionally, the seals may be subject to wear caused by various conditions, such as startup, transients, upsets, and shutdowns, thus, causing downtime and additional costs to replace the seals. Alternatively, the seals may be designed with increased leakage to extend their life, but with the disadvantage of decreased efficiency and performance of the turbomachine.